1. Field of the Invention
The invention relates to a method for individual transfer of offset printing plates from a magazine in which they are supported on their respective edges and stacked each with its non-coated side facing upwards, to a receiving table receiving a plate with its non-coated side facing downwards, and where the uppermost plate of the stack is gripped by means of a gripping means engaging the non-coated side of the plate in such a manner that said plate is retained by the gripping means during the transfer to the receiving table.
2. Background Art
EP-PS No. 0 037 064 discloses an apparatus for individual transport of printing plates. The printing plates are stacked in an inclined magazine with each with its non-coated side facing outwards and with intermediary protecting sheets arranged adjacent plates. The printing plates are transferred one by one from the magazine to a horizontally arranged conveyor advancing each plate to an exposure station. The apparatus comprises a pivotally arranged lifting cylinder, the displaceable piston rod of which is provided with suction means for gripping the uppermost plate in the stack and retaining that plate during the transfer to the conveyor. When a plate is to be gripped, the lifting cylinder is turned downwards into a position in which the piston rod thereof is arranged substantially perpendicular to the stack of plates. Subsequently, the piston rod is moved forwards until the suction means abut the surface of the uppermost plate. Then, the suction means are subjected to a vacuum in such a manner that they grip the plate, whereafter the piston rod is retracted in the cylinder until the plate has been slightly lifted from the plate therebelow. Then, pressurized air is blown between the plate lifted and the plate now on top of the stack, in such a manner that the protecting sheet is removed. Finally, the lifting cylinder is turned to its vertical position, with the effect that the plate levels with the conveyor path. When vacuum is no longer fed to the suction cups, the conveyor can advance the plates to the exposure station. The protecting sheets between the plates prevent the uppermost plate from adhering to the plate therebelow when said uppermost plate is being lifted from the stack. In addition, the protecting sheets protect, of course, the light-sensitive sides of the plates from being scratched when two plates are displaced relative to one another. The method and the apparatus of this prior art publication suffer, however, from the drawback of being rather complicated, partly due to the multitude of movements necessitating a multitude of mechanisms and partly due to the use of protecting sheets between the plates in the stack.